Phase change materials, also known as latent heat-storage materials, may store and release heat energy within a slight change in temperature or no change in temperature. These materials may find application in temperature-regulating textiles, solar energy storing, smart housing, agricultural greenhouses, heat management of electronics, telecommunications and microprocessor equipment, and biomedical products.
Existing organic, inorganic, polymeric, and eutectic phase change materials may have latent heat storage properties. When the temperature of these materials is raised above the phase change temperature, energy may be absorbed and may be used to convert the solid structure into a liquid. Heat may be absorbed during the phase change while the temperature remains constant. When these materials are cooled down, the latent heat may be released into the surrounding environment. However, these conventional phase change materials are not suitable for use as temperature-regulating fibers, because these materials typically become a liquid when heated above the phase change temperature, which would cause a loss of fiber structure and integrity.
Attempts have been made to prepare temperature-regulating fibers by incorporating microencapsulated phase change materials into fibers during wet spinning or melt spinning process. However, experimental results have exposed several disadvantages in this method. First, microcapsules may form clusters and may cause discontinuity in the spinning process. Second, the thermal capacity of the prepared fibers is unsatisfactorily low, typically about 8 to 12 J/g, because there is an upper loading limit for the microencapsulated phase change materials. Third, incorporating phase change materials into melt spun fibers can be difficult, because phase change materials typically are volatile materials that may be unfit for high temperature extrusion and pumping processes.
Physical blending of long chain polymeric phase change materials with other fiber-forming polymers, such as polypropylene and polyester, has been used to fabricate temperature-regulating fibers. However, the fibers as prepared may have a tendency to lose their phase change characteristics after only several heating-cooling cycles.
It is therefore desirable to develop a fiber that can be used for temperature regulation. It is also desirable to develop a fiber that has a shape memory effect and good physical properties. It is further desirable to develop a simple and effective method of making fibers having these properties.